Visiting other planets is a dream that most of us alive today will have to experience vicariously through probes like the plucky NASA Mars rovers, which have sent a thousand photo albums' worth of snapshots back to Earth. But here's what most people don't realize: you can get a feel for visiting other worlds just by going to certain places on our own planet.
Scientists have sought out these planetary proxies for years, attempting to understand whether life might arise in such desolate environments, and how we would know it if it did. Ellesmere Island
, a rocky expanse of glaciers and mountains off the coast of Greenland, bears remarkable similarities to a far-off moon, and it hosts a peculiar kind of bacteria that extracts the oxygen it needs to live from sulfate minerals in surrounding ice
. Scientists believe that similar organisms might thrive on Europa
, a moon orbiting Jupiter that is thought to have liquid oceans beneath a surface of ice. If Europa is indeed home to such psychrophiles (living things that thrive in extreme cold), studying them here on Earth might make it easier to detect them with NASA probes in the future.
Sometimes lifelessness, however, is just as useful. When scientists performed the life-seeking experiments that the Viking spacecraft performed on Mars in the 1970s, they found, just as they had on Mars, no signs of life at all. It was a remarkable finding: "The Atacama," the principal investigator said at the time, "appears to be the only place on Earth Viking would have found nothing."
Another extreme, but surprisingly lively, environment can be found in Antarctica's Dry Valleys, which are some of the most inhospitable places on Earth: temperatures have fallen as low as -90 degrees Fahrenheit, and winds can blow up to 200 mph. They still host hardy organisms like lichens, mosses, and nematodes that can survive the brutal conditions. Scientists believe that, like the lifeless Atacama, these valleys resemble the environment on Mars; studying how creatures nevertheless manage to survive there could give insight into how life might exist on the Red Planet.
These extreme environments are frequented not just by hardy bacteria and lichens, but also by scientists. In areas that resemble Mars, look for the telltale signs of the Mars Society, a non-profit group that encourages research into exploration of the Red Planet and has built Mars Desert Research Stations in Australia, Iceland, the Canadian Arctic, as well as this one, near Hanksville, Utah.
Mars is one of the planets where life might have once taken hold, and is thus subject to intense scrutiny. The vast majority of planetary proxies are attempts to simulate and understand the environment there, in order to guide the search for past or present Martian life, as well as aiding in understanding Mars' geological history. The Mars Society gives geologists, astrobiologists, and engineers a chance to train and test equipment for those missions. If they can test rovers and instruments in the most realistic way possible, the more likely it is that when probes and, eventually, astronauts land on Mars, they'll be able to recognize any signs of Martian life, for instance.
Engineering projects intended for interplanetary travel, like this six-legged rover meant to carry heavy loads across the surface of a distant moon or planet, can also be found gallivanting across Earth's deserts. The desert outside Flagstaff, Arizona, was the proving grounds for this rover, called ATHLETE--All-Terrain Hex-Legged Extra-Terrestrial Explorer--which someday might transport living quarters for astronauts.
Deserts are not the only otherwordly places on Earth. Astronauts can train for space missions in underwater environments like the enormous Neutral Buoyancy Laboratory, located in NASA's Johnson Space Center. But these huge bathtubs do not always accurately simulate the trials of space missions: for instance, astronauts can't live in modules at the bottom of these tubs for days on end. That's when NASA turns to the Aquarius Underwater Laboratory. Located 60 feet below the surface of the Atlantic Ocean near Key Largo, it lets spacewalkers work with support crews and a mission control. These particular astronauts are participating in NEEMO 15, the latest NASA Extreme Environment Mission Operations voyage; they are helping NASA determine the best way to send a manned crew to an asteroid.
Sometimes, retreating to the dryness and security of a landlubber's lab is the best way to understand what's happening on a planet far, far away. For instance, when the Phoenix spacecraft landed on Mars in 2008, it kicked up enough dust to reveal water ice--a surprise to its builders, who hadn't thought that the lander's relatively weak rocket engines could have moved so much material. To find out what happened, astrophysicists at NASA's Ames facility devised an artificial environment full of crushed walnut shells to test the engines and found that the pulsing of the rockets on the Martian surface injected more gas into the soil than expected. The gas then burst out of the soil in explosive puffs, causing erosion.
There are times when artificial environments in labs can become, well, hellish. This ominous-looking black hole in the ground leads to the Large Space Simulator, a special facility in the Netherlands built by the European Space Agency. It can simulate the punishing conditions a spacecraft would encounter near Mercury, a planet so close to the Sun that it takes only 88 days to complete an orbit. This image shows a part of the ESA's BepiColombo spacecraft after it has been subjected to temperatures higher than 660 degrees Fahrenheit, which it will face while spying on the solar system's innermost planet.
Simulating the conditions on Venus is also a tall order, but scientists are attempting it with the Extreme Environment Test Chamber, at NASA's Glenn Research Center in Cleveland, Ohio. This beast can simulate the mind-boggling conditions on the surface of Venus: it is able to create pressures of 1,350 pounds per square inch--90 times Earth's air pressure at sea level--and temperatures of 1,000 degrees Fahrenheit. This device can also subject test devices to lethal gases like hydrogen fluoride, sulfur dioxide, and hydrogen chloride, all of which exist in Venus' atmosphere and to which future probes will be exposed. This is definitely one planet where astronauts won't be landing anytime soon.